used as a conventional title of courtesy before a man's surname
used in direct address before a man's title of office
May I ask one more question, Mr Chairman?
used before the name of a place or of a profession or activity or before some epithet to form a title applied to a male viewed or recognized as a representative of the thing indicated
Here comes Mr Football
[Middle English, abbr of maister master; Messrs abbr of French Messieurs, pl of Monsieur]